Magnetic gears are known and typically involve a concentric array of annular components that rotate relative to one another in order to rotate an output shaft at a different speed to an input shaft.
In one type of configuration, an inner permanent magnet can form an inner rotor and an outer permanent magnet can form an outer stator. A rotational pole-piece structure can be located between the inner and outer permanent magnets in order to provide a concentration of magnetic lines of force therebetween, and modulate the magnetic field so as to produce a gearing between the input and output shafts. The pole-piece structure forms a torque path between the input and output shafts without any mechanical contact. It is possible to vary the arrangement such that the pole-piece is a stator, and the two sets of permanent magnets rotate.
The gear ratio may be equal to the number of magnetic pole pairs on the permanent magnet associated with the high speed shaft, as compared to the number of magnetic pole pairs on the permanent magnet associated with the low speed shaft. This implies an even number of permanent magnets associated with each shaft.
Magnetic gears have known advantages in that, although bearings are required to mount the shafts in the gear assembly, the coupling between the moving parts is otherwise frictionless.
Pole-pieces, or “modulators” may be formed from laminate plates. Typically these are held together by a chassis or sub-carriage that extends through air gaps in the pole-piece. It is desired to provide improvements to the mounting of the pole-piece to the high or low speed shaft, or to the housing.